This invention relates to the control of a dual mode drive arrangement for an automotive refrigerant compressor.
Dual mode compressor drive arrangements have been utilized to maintain continuous climate control operation in automotive powertrains, with the dual mode drive arrangement allowing a refrigerant compressor of the climate control system to be selectively driven by the powertrain internal combustion engine or an electric motor. For example, the engine may be coupled to the compressor drive shaft through an electromagnetic clutch, and the armature of the electric motor may be coupled to (or integral with) the compressor drive shaft. Typically, the drive arrangement is configured so that the compressor is driven by the engine when the engine is running, and by the electric motor when the engine is not running. For example, if the engine is turned off under idle conditions to reduce fuel consumption, the electric motor may be activated to prevent interruption of the compressor drive. Similar considerations occur in hybrid powertrain configurations where the vehicle is selectively driven by an engine or an electric drive motor, or where an engine is intermittently operated to provide supplemental electric power to an electric drive motor.
The present invention is directed to an improved control method for a dual mode drive arrangement coupling a climate control compressor to an electric machine and an engine, where the engine is turned on and off during operation of the vehicle, and where the electric machine is selectively operated as a motor or a generator during operation of the engine for improved efficiency and performance. In a preferred embodiment, the machine is operated as a generator to increase the available power for vehicle electrical loads when compressor operation is not needed or when the engine is driving the compressor. Conversely, the machine is operated as a motor to drive the compressor under heavy engine loading or when the engine speed is outside a desired operating range defined in terms of compressor speed.